Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 210000 | Metric tons, gross weight | NA |
| 2003 | 357000 | Metric tons, gross weight | 70.00% |
| 2004 | 454000 | Metric tons, gross weight | 27.17% |
| 2005 | 578000 | Metric tons, gross weight | 27.31% |
| 2006 | 600000 | Metric tons, gross weight | 3.81% |
